Steering wheel

ABSTRACT

An automotive steering wheel includes a heavy air bag system held by a horn-switching mechanism. Although the air bag system is heavy, the operator has a good feel for the operation of the horn-switching mechanism. The horn-switching mechanism includes a stationary member, a movable member, a switch main body, coil springs, and a jawed bolt. The switch main body comprises a stationary contact mounted on the stationary member and a movable contact mounted on the movable member. The coil springs bias the movable member upward. The jawed bolt permits the movable member to be moved toward the stationary member and limits the distance of the movable member from the stationary member. At least one of the coil springs is located at a height substantially equal to the height of the resultant center of gravity of all components biased upward by all the coil springs.

This application is a divisional of U.S. application Ser. No.09/659,338, filed Sep. 12, 2000 now U.S. Pat. No. 6,299,201, which is acontinuation of U.S. application Ser. No. 08/906,827, filed Aug. 6,1997, now U.S. Pat. No. 6,139,051.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a steering wheel mounted in a vehicleand, particularly, to a steering wheel equipped with an air bag system.More particularly, the invention relates to a steering wheel includingan air bag system supported by horn-switching mechanisms.

2. Description of the Related Art

A known steering wheel of this kind is described, for example, inJapanese Utility Model Unexamined Publication No. 143734/1990 and shownin FIG. 1. This steering wheel, generally indicated by WO, has a wheelmain body 1. An air bag system 4 is mounted at the top of the centralportion of the wheel main body 1. Each horn-switching mechanism 10 islocated between the wheel main body 1 and the air bag system 4. Thewheel main body 1 includes part of the steering wheel WO and excludesthe air bag system 4 and the horn-switching mechanisms 10.

The air bag system 4 is composed of an air bag 5, an inflator 6, a pad7, and a bag holder 8. The air bag 5 is folded so that it is capable ofinflating. The inflator 6 supplies a gas used to inflate the air bag 5.The pad 7 covers the folded air bag 5. The bag holder 8 holds the airbag 5, the inflator 6, and the pad 7.

The horn-switching mechanisms 10 are located under the bag holder 8 atopposite sides, respectively, of the holder 8 and extend forward andrearward. FIG. 1 is a cross-sectional view of the steering wheel WO,taken in the longitudinal direction and in the front and rear direction.

Each horn-switching mechanism 10 comprises a stationary member 11, amovable member 12, a coil spring 16, and a jawed bolt 19. The stationarymember 11 consists of a metal plate and is connected with a metal core 2forming the steering wheel main body 1. Fixed contacts 14 are mounted tothe front and rear ends, respectively, of the stationary member 11. Themovable member 12 is made of a metal plate and located above thestationary member 11. Movable contacts 15 are positioned at the frontand rear ends, respectively, of the movable member 12. The coil spring16 is positioned between the movable member 12 and the stationary member11 and forms a means for biasing the movable member 12 upward. The jawedbolt 19 forms a means for limiting the distance by which the movablemember 12 is spaced from the stationary member 11. The jawed bolt 19 isscrewed to the metal core 2 from above the movable member 12.

A lead wire (not shown) is connected with each movable member 12 of thehorn-switching mechanisms 10 so that the movable member 12 iselectrically connected with the positive side of the horn-activatingcircuit. Each stationary member 11 is electrically connected with thenegative side of the horn-activating circuit via the metal core 2.

The fixed contacts 14 and the movable contacts 15 together form a switchmain body 13.

Insulating spacers 17, 18 and rubber rings 20 electrically insulate themovable members 12 from the stationary members 11 when they are incontact with both the coil springs 16 and the jawed bolts 19.

Each movable member 12 has a mounting member (not shown) attachedthereto permitting the bag holder 8 to be secured with bolts.

In the prior art steering wheel WO, the horn-switching mechanisms 10 arelocated on opposite sides of, and under, the heavy air bag system 4.That is, the air bag system 4 of the prior art steering wheel WO isswingably supported by the coil springs 16 of the horn-switchingmechanisms 10 that are at opposite sides of, and under, the air bagsystem 4.

When the coil springs 16, used to bias the horn-switching mechanisms 10of the prior art steering wheel WO, have a low spring constant, thehorn-switching mechanisms 10 may be inadvertently activated because theheavy air bag system 4 can easily tilt or swing horizontally due tovibrations of the vehicle.

More specifically, in the prior art steering wheel WO, the air bagsystem 4 and the movable member 12 are held upwardly by all the coilsprings 16. In the illustrated example, four coil springs are used. Theposition of the resultant center of gravity G of these supported members(the air bag system 4 and the movable member 12) is higher than the coilsprings 16 by as much as 30 mm. With the forward coil spring 16F placedat the center of a rotation moment, a rotation moment, P×L, acts on therear coil spring 16B, where P is the force of a rearward swingingmovement at the side of the center of gravity G and L is the distancebetween the center of gravity G and the coil spring 16F in the directionof height. The rotation moment, P×L, compresses the coil spring 16B andbrings the rear movable contact 15B into contact with the fixed contact14B. As a result, the switch main body 13B is electrically activated.

Accordingly, the coil springs 16 biasing the horn-switching mechanisms10 have high spring constants. However, when coil springs having highspring constants are used, as in the coil springs 16, a larger load mustbe applied to manually activate the horn-switching mechanisms 10. Thisdeteriorates the feel for the horn-switching mechanisms experienced bythe driver when the horn-switching mechanisms 10 are operated.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a steering wheelhaving horn-switching mechanisms which hold a heavy air bag system butgive the driver a good feel for the manual operation of thehorn-switching mechanisms.

This object is achieved by a steering wheel comprising a horn-switchingmechanism and an air bag system held on top of the main body of thesteering wheel by the horn-switching mechanism. The horn-switchingmechanism comprises a stationary member, a movable member, plural switchmain bodies, plural biasing means, and plural limiting members. Thestationary member is located under the horn-switching mechanism andconnected to the main body of the steering wheel. The movable member ispositioned over the horn-switching mechanism and supports the air bagsystem.

Each switch main body comprises a stationary contact mounted on thestationary member and a movable contact mounted on the movable member.The biasing means are mounted between the stationary member and themovable member and act to bias the movable member upwardly. The limitingmembers connect the stationary and movable members so that the movablemember can move toward the stationary member and limit the distance ofthe movable member from the stationary member. At least one of thebiasing means is located at a height substantially equal to the heightof the resultant center of gravity of all components that are biasedupwardly.

It is desired that at least one biasing means be located at a heightsubstantially equal to the height of the resultant center of gravity ofall components that are biased upwardly and preferably has a verticalcenter that is substantially coincident with the height of the resultantcenter of gravity. Also, it is desired that all the biasing means belocated at a height substantially equal to the resultant center ofgravity of the components that are biased upwardly.

In the steering wheel in accordance with the invention, at least onebiasing means is located at a height substantially equal to the heightof the resultant center of gravity of all the components that are biasedupwardly. Therefore, if one biasing means is not disposed around theheight of the resultant center of gravity but is located at the centerof the rotation moment, the rotation moment, P×L, acts on the biasingmeans located near the height of the resultant center of gravity, whereP is the force of a horizontal swinging movement acting on the center ofgravity G of the air bag system and L is the distance between the centerof gravity G and the biasing means located near the height of the centerof gravity.

This rotation moment, P×L, barely compresses the biasing means locatednear the height of the center of gravity because L is close to zero.Therefore, inadvertent activation of the switch main bodies to operatethe horn can be prevented. In addition, the load needed to manuallyoperate the horn-switching mechanisms is reduced because biasing meanswith lower spring constants may be used or the number of the biasingmeans may be reduced.

Accordingly, in the steering wheel in accordance with the invention, ifa heavy air bag system is mounted to the horn-switching mechanisms, theload applied to manually operate the horn-switching mechanisms may bereduced. This can improve the feel experienced by the operator when thehorn-switching mechanisms are operated.

The center of the biasing means is located near the height of the centerof gravity of the air bag, system. The above-described distance L canbecome close to zero by placing, this center of the biasing means at theheight of the center of gravity. Consequently, the load required tooperate the horn-switching mechanisms may be reduced further by usingbiasing means having, lower spring constants.

When all the biasing means are located near the height of the center ofgravity of the air bag system, all the rotation moments produced aboutthe biasing means can be reduced to nearly zero. In consequence, theload required to manually operate the horn-switching mechanisms may bedecreased further by using biasing means of lower spring constants. Thismay contribute to further improvement of the feel experienced by theoperation when operating the horn-switching mechanisms.

Other objects and features of the invention will appear in the course ofthe description thereof which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the prior art steering wheel;

FIG. 2 is a cross-sectional view of a steering wheel in accordance withthe invention, taken along line II—II of FIG. 4;

FIG. 3 is a cross-sectional view of the steering wheel shown in FIG. 2,taken along line III—III of FIG. 4;

FIG. 4 is a plan view of the steering wheel shown in FIG. 2;

FIG. 5 is a plan view of a support plate holding a stationary memberused in the steering wheel shown in FIG. 4;

FIG. 6 is an exploded perspective view of a switch subassembly used inthe steering wheel shown in FIG. 4; and

FIG. 7 is a partial cutaway of the front elevation of the switchsubassembly shown in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the preferred embodiments of the invention are hereafter describedwith reference to the accompanying drawings, it should be understoodthat the invention is not limited thereto but rather various changes andmodifications are possible within the scope of the invention that isdelineated by the accompanying claims.

Referring to FIGS. 2-4, there is shown a steering wheel embodying theconcept of the present invention. This steering wheel, generallyindicated by W1, comprises an annular portion R, a boss portion Blocated in the center of the annular portion R, and three spokes Sconnecting the annular portion R with the boss portion B. In terms ofcomponents, the steering wheel W1 is composed of a steering wheel mainbody 21, an air bag system 30, and at least one horn-switching mechanism40 with this being shown in FIG. 2. The air bag system 30 is located ontop of the boss portion B. The horn-switching mechanism 40 is connectedto the body 21 of the steering wheel and holds the air bag system 30.

The steering wheel main body 21 is part of the steering wheel WIexcluding the air bag system 30 and the horn-switching mechanism 40. Themain body 21 of the steering wheel has a metal core 22 that connects theannular Portion R, the boss portion B, and the spokes S. The metal core22 has a core portion 23 located at the annular portion and coreportions 25 that are located at the spokes and at the side of the coreportion 23. These core portions 23 and 25 are coated with a coatinglayer 26 of a synthetic resin. A metal core 24 at the location of theboss portion B is composed of a boss 24 a and a coating portion 24 b.The boss 24 a is made of steel and connected to the steering shaft (notshown). The coating portion 24 b is made of an aluminum alloy or thelike and surrounds the boss 24 a. The coating portion 24 b is formedintegrally with the core portions 23 and 25. A rear metal core 25B atthe spoke locations bifurcates and connects to the coating portion 24 bof the metal core 24 of the boss portion. The main body 21 of thesteering wheel has a lower cover 27 that covers the bottom of the bossportion B. The lower cover 27 is screwed to the metal core 22.

The air bag system 30 comprises an air bag 31, an inflator 33, a pad 34,and a bag holder 35. The air bag 31 is folded so as to be inflatable.The inflator 33 supplies a gas used for inflation into the air bag 31.The pad 34 covers the folded air bag 31. The bag holder 35 holds the airbag 31, the inflator 33, and the pad 34.

The inflator 33 comprises a substantially cylindrical body 33 a and aflange 33 c. A gas discharge port 33 b is formed at the top of the body33 a. The flange 33 c protrudes from the outer surface of the body 33 a.

The pad 34 is made of a synthetic resin and comprises a top wall portion34 a and a side wall portion 34 b. When the air bag 31 inflates, the topwall portion 34 a breaks at a given location. The side wall portion 34 bis substantially hexagonally shaped at its perimeter and extendsdownwardly from around the outer surface of the top wall portion 34 a.The side wall portion 34 b has an engaging groove 34 c formed at a givenposition in the inner surface. The bag holder 35 has side wall portions37 provided with engaging claws 37 a (described later). These claws 37 aengage the fringes of the engaging groove 34 c. Ribs (bearing noreference numeral) are formed on the bottom surface of the top wallportion 34 a. These ribs bear against mounting portions 39 (describedlater) of the bag holder 35.

The bag holder 35 holds the air bag 31 and the inflator 33 by using anannular retainer 32, which has a plurality of bolts (not shown)extending downward. These bolts pass through the air bag 31, the bagholder 35, and the flange 33 c of the inflator 33. Nuts are screwed tothe bolts so that the air bag 31 and the inflator 33 are held by the bagholder 35. The side wall portion 34 b is mounted with rivets so that thebag 34 is held by the bag holder 35.

The bag holder 35 is a made of metal plate and comprises a lateral plateportion 36, side wall portions 37, and three interconnecting plateportions 38. The lateral plate portion 36 has a centrally providedinsertion hole 36 a into which the body 33 a of the inflator can beinserted from below. The side wall portions 37 extend from both sides ofthe front and rear fringes, respectively, of the lateral plate portion36 and take a V-shaped form in cross section. The three interconnectingplate portions 38 extend upward from right and left side fringes andfrom the rear fringe, respectively.

Each side wall portion 37 is provided with an engaging claw 37 ainterlocked in the groove 34 c located in the pad side wall portion 34b. Each side wall portion 37 is formed with mounting, holes (not shown)used to mount the pad side wall portion 34 b with rivets.

The mounting portions 39 extending outwardly and laterally are formed atthe top ends of the interconnecting plate portions 38. Nuts 39 b arewelded to the mounting portions 39, which are provided with mountingholes 39 a. At the positions of the mounting portions 39, the air bagsystem 30 is connected to the horn-switching mechanism 40. Thesemounting portions 39 form parts of a movable member 48 of thehorn-switching mechanism 40. Lead wires (not shown) are connected withthe bag holder 35 to electrically connect the holder with the positiveside of the horn-activating circuit.

The horn-switching mechanism 40, which is shown in exploded form in FIG.6, comprises a stationary member 41, the movable member 48, a switchmain body 50, a coil spring 55, and a jawed bolt 56. The stationarymember 41 is connected to the metal core 25 in the spoke portions. Themovable member 48 is located above the stationary member 41. The switchmain body 50 comprises a stationary contact member 51 and a movablecontact member 53 which include a stationary contact 52 and a movablecontact 54, respectively. The coil spring 55, which acts as a biasingmeans, is disposed between the stationary member 41 and the movablemember 48 and biases the movable member 48 upwardly. The jawed bolt 56allows the movable member 48 to move toward the stationary member 41 andacts as a means for limiting the distance of the movable member 48 fromthe stationary member 41.

In the illustrated embodiment, the stationary member 41 comprises asupport plate 42 and a support grommet 47.

The support plate 42 is mounted to a left spoke portion metal core 25Land a right spoke portion metal core 25R with bolts 58. The supportplate 42 is made of a metal plate and comprises a connecting rod portion43, shown in FIG. 5, and support base portions 44, as shown in FIGS. 2,3, and 5. The connecting rod portion 43 has a U-shaped form in a planeview (see FIG. 5). The support base portions 44 extend upwardly from theleft fringe, the right fringe, and the rear fringe, respectively, of theconnecting rod portion 43 and extend outwardly from their top ends.

Each support base portion 44 comprises vertical plate portions 44 a andbase body portions 44 b. The vertical plate portions 44 a extendupwardly from the connecting rod portion 43. The base body portions 44 bextend outwardly from the top ends of the vertical plate portion 44 a.Each base body portion 44 b has centrally provided mounting hole 44 c.This hole 44 c consists principally of a circular hole with the inclinesof right-angled triangles attached to its opposite fringes that are insymmetrical positions. Each base body portion 44 b has small circularengaging holes 44 d on opposite sides of the mounting hole 44 c.

Connecting portions 45 descend obliquely from around the right and leftvertical plate portions 44 a of the connecting rod portions 43. Nuts 46are firmly secured to the connecting portions 45 to mount the supportslate 42 to the left spoke portion metal core 25L and the right spokeportion metal core 25R with the bolts 58.

As shown in FIGS. 6 and 7, the support grommet 47 is substantiallycylindrical in shape and made of an insulating synthetic resin such aspolyacetal. An engaging plate portion 47 a conforming to the shape ofthe opening in the mounting hole 44 c in each support base portion 44 ismounted to the bottom of the support grommet 47. This grommet 47 has arecess 47 c corresponding to the arc-shaped portion of the mounting hole44 c, the recess 47 c being located over the engaging plate portion 47a. A protrusion 47 b is formed on the top surface of the engaging plateportion 47 a and is inserted in the engaging hole 44 d. A pair ofengaging step portions 47 d and a pair of recesses 47 e are formed atsymmetrical positions in the outer surface of the support grommet 47.The stationary contact members 51 (described further below) are engagedat the positions of the engaging step portions 47 d. Insulating spacers49 have engaging claws 49 b and are placed in the recesses 47 e,respectively, so as to be movable downwardly.

The stationary contact member 51 is made of spring steel and includes astationary contact 52, engaging portions 51 a, and spring portions 51 c.The stationary contact 52 is preferably annular in shape. The engagingportions 51 a extend downwardly from symmetrical positions on the outerfringe of the stationary contact 52. Each spring portion 51 c extendsdownward from the bottom end of the corresponding engaging portion 51 aand is curved. The engaging portions 51 a have inwardly protrudingengaging claws 51 b that engage the engaging step portions 47 d,respectively, of the support grommet 47. When the support grommet 47 ismounted to the support base portion 44 with a bayonet-type fitting, thespring portions 51 c of the stationary contact member 51 push againstthe fringes of the mounting holes 44 c on the top surfaces of the basebody portions 44 b of the support base portion 44.

The spring portions 51 c of the stationary contact member 51 press thetop surfaces of the engaging plate portions 47 a against the fringes ofthe mounting holes 44 c on the lower surfaces of the base body grommet47 is mounted with portions 44 b. When the support grommet 47 is mountedwith the bayonet fitting, the engaging plate portions 47 a are insertedinto the mounting holes 44 c in the support base portions 44 from above.Then, the grommet 47 is rotated through 90°. The protrusion 47 b on theengaging plate portion 47 a is inserted into the engaging hole 44 d inthe support base portion 44.

When the engaging claws 51 b of the stationary contact member 51 areengaged with the engaging step portions 47 d of the support grommet 47,the stationary contact 52 rests on the top end surface of the grommet47. When the support plate 42 is mounted to the left spoke portion metalcore 25L and the right spoke portion metal core 25R with the bolts 58,the stationary contact 52 of the stationary contact member 51 iselectrically connected with the negative side of the horn-activatingcircuit throughout the spring portion 51 c of the stationary contactmember 51, the support plate 42, and the metal cores 25R, 25L.

In the illustrated embodiment, the movable member 48 comprises themounting portions 39 of the bag holder 35 and insulating spacers 49.

These insulating spacers 49 are substantially cylindrical in shape andmade of a synthetic resin, having insulation qualities, such aspolyacetal. As shown in FIGS. 6 and 7, each insulating spacer 49comprises a spring seat 49 a, two engaging claws 49 b, and threeengaging step portions 49 c. The spring seat 49 a protrudes like a jawfrom the top outer surface. The engaging claws 49 b protrude downwardfrom the bottom of the spring seat 49 a. The engaging step portions 49 care formed on the inner surfaces of the spring seat 49 a. The engagingclaws 49 b are placed in the recesses 47 e formed in the support grommet47, allowed to move downwardly toward the annular stationary contact 52of the stationary contact member 51, and engage with the contact 52. Theengaging step portions 49 c inhibit movement of a movable contact member53.

The movable contact member 53 is made of spring steel and comprises anannular base portion 53 a, three engaging portions 53 b, and movablecontacts 54. The engaging portions 53 b extend downward from the outersurface of the base portion 53 a. The movable contacts 54 extendoutwardly from the bottom ends of the engaging portions 53 b. Engagingclaws 53 c, for engaging the engaging step portions 49 c of theinsulating spacer 49, protrude outwardly from the engaging portions 53b.

When the engaging claws 53 c of the movable contact member 53 areanchored to the engaging step portions 49 c of the insulating spacers49, the movable contacts 54 are placed on the bottom surfaces of theinsulating spacers 49.

In the illustrated embodiment, the support grommet 47, the insulatingspacer 49, and the coil springs 55, together with the stationary contact52 and the movable contact 54 forming the switch main body 50, arepre-assembled into a switch subassembly H shown in FIG. 4. Thissubassembly H is fabricated in a manner described below. First, thestationary contact member 51 is mounted to the support grommet 47, andthe movable contact member 53 is mounted to the insulating spacer 49.Then, the lower ends of the coil springs 55 are made to bear against theengaging plate portions 47 a of the grommet 47. The top ends of the coilsprings 55 are abutted against the spring seats 49 a of the insulatingspacers 49. The engaging claws 49 b of the spacers 49 are then insertedinto the recesses 47 e in the grommet 47 and are engaged to thestationary contact 52 of the stationary contact member 51. Thus, theswitch subassembly H is completed. Since the subassembly H is easy tohandle, the horn-switching mechanisms 40 can be easily assembled.

In this embodiment, the switch subassembly H forms the horn-switchingmechanisms 40 which in turn support the air bag system 30. First, theengaging plate portions 47 a of the support grommet 47 of each switchsubassembly H are inserted into the mounting holes 44 c in the base bodyportions 44 b of the support base portion 44 of the support plate 42 andmounted with a bayonet fitting. The mounting portions 39 of the backholder 35 of the air bag system 30 assembled previously are placed aboveeach switch subassembly H. The jawed bolts 56 are inserted into theswitch subassemblies H from below and screwed to the nuts 39 b of themounting portions 39, thus forming the horn-switching mechanism 40. Thishorn-switching mechanism 40 supports the air bag system 30. Thehorn-switching mechanism 40 and the air bag system 30 are assembled intoa subassembly which can be easily mounted to the main body 21 of thesteering wheel.

The air bag system 30 is assembled in the manner described below. Theretainer 32 is placed in the air bag 31. The air bag 31 is then folded.Bolts (not shown), extending from the retainer, are passed through thebag holder 35 and through the flange 33 c of the inflator and securedthere with nuts. The engaging claws 37 a of the side wall portions 37 ofthe bag holder are engaged in the engaging grooves 34 c in the pad sidewall portions 34 b. The pad side wall portions 34 b are riveted to theside wall portions 37 of the bag holder, thus completing the air bagsystem 30.

After supporting the air bag system 30 on the horn-switching mechanisms40, connecting portions 45 of the support plate 42 of the horn-switchingmechanisms 40 are made to bear against the left spoke portion metal core25L and the right spoke portion metal core 25R. From the rear side ofthe metal cores 25L and 25R, the bolts 58 are screwed to the nuts 46 ofthe connecting portions 45. Thus, the horn-switching mechanisms 40 canbe connected to the body 21 of the steering wheel. Consequently, thesteering wheel W1 may be assembled.

The boss 24 a on the boss portion metal cores 24 of the steering wheelmain body 21 has been previously connected to the steering shaft of thevehicle.

When the jawed bolt 56 is screwed to the nut 39 b, the movable contact53 of each switch subassembly H is pushed by an enlarged portion 56 a ofthe bolt 56, so that the base portion 53 a of the movable contact member53 is pressed against the fringe of the mounting hole 39 a of themounting portion 39 of the bag holder 35. As a result, the movablecontact 53 of each switch subassembly H is electrically connected withthe positive side of the horn activating circuit through the lead wires(not shown). When the support plate 42 is secured to the metal cores 25Land 25R of the spokes with the bolts 58, the stationary contact 52 ofeach switch subassembly H is electrically connected with the negativeside of the horn-activating circuit through the spring portion 51 c ofthe stationary contact member 51, the support plate 42 and the metalcores 25L and 25R.

In the present embodiment, when each horn-switching mechanism 40 isconnected with the main body 21 of the steering wheel in this manner,the outwardly extending front end portions of the base body portions 44b of the support base portion 44 of the support plate 42 forming thestationary member 41 bear against the coating layer 26 on the metalcores 25 of the spokes of the wheel main body. Thus, the base bodyportions are supported.

In the illustrated embodiment, the base body portions 44 b of thesupport base portion 44 of the support plate 42 and the mountingportions 39 of the bag holder 35 are placed close to the coating layer26 of each spoke S. Consequently, the coil springs 55 of each switchsubassembly H are so positioned that the vertical center of each coilspring 55 is coincident with the height of the resultant center ofgravity G of the components biased upwardly by all the coil springs 55.The components biased upwardly by all the coil springs 55 are the airbag system 30 (air bag 31, retainer 32, inflator 33, pad 34, bag holder35, lead wires, etc.), the movable member 48 (mounting portions 39,insulating spacer 49, and movable contact member 53), and the jawedbolts 56.

Therefore, in the steering wheel WI of the present embodiment, if onecoil spring 55B is placed at the center of a rotation moment as shown inFIG. 2, a rotation moment, P×L, acts on the coil spring 55A, where P isthe force of a horizontal swinging movement acting at the center ofgravity G (such as of the air bag system 30) and L is the distancebetween the height of the center of gravity G and the height of the coilspring 55A located at the center of gravity G. Since the distance L isnearly zero, the rotation moment, P×L, barely compresses the coil spring55A. For this reason, even if the coil spring 55A does not have a highspring constant, the switch body 50 is prevented from beinginadvertently activated. In addition, coil springs with lower springconstants can be used at the other coil springs 55B and 56C, because therotation moment due to swinging movement of the air bag system 30 issmall.

Accordingly, in the case of the steering wheel WI of the presentembodiment, if the heavy air bag system 30 is held by the horn-switchingmechanisms 40, a coil spring of a low spring constant can be used as thecoil spring 55. This can improve the driver's feel for thehorn-switching mechanisms 40 when operated. In this embodiment, if theair bag system 30 is as heavy as the prior art air bag system, the loadthat needs to be applied to manually operate the horn may be reduced totwo thirds of the load required in the prior art bag systems.

Usually, the horn is operated by depressing the top wall portion 34 a ofthe pad 34 of the air bag system 30. At this time, the coil spring 55 ofeach switch subassembly H is compressed, bringing the movable contact 54of the movable contact member 53 forming the switch body 50 into contactwith the stationary contact 52 of the stationary contact material 51,thus activating the horn.

In the embodiment described above, the vertical center of all the coilsprings 55 of the horn-switching mechanism 40 is made coincident withthe height of the center of gravity G of the components biased upwardlyby all the coil springs 55. The height of each switch subassembly H maybe shifted so that the center of gravity G lies within the limitsdefined by the upper and lower ends of each coil springs 55. Thisstructure yields less advantages than the above-described embodiment butthe load that must be applied to operate the horn-switching mechanism 40can be made smaller than in conventional systems.

Furthermore, the center of gravity G may be placed between the upper andlower ends of at least one coil spring 55; the center of gravity G isnot placed between the upper and lower ends of any other coil spring 55.In this way, the produced advantages are less conspicuous than in theabove-described embodiment, but the load that must be applied to operatethe horn-switching mechanism 40 can be smaller than before.

If at least one coil spring 55 is placed at a height substantially equalto the height of the center of gravity G (in other words, at least onecoil spring 55 is placed within the steering wheel, and the distance ofthe height of the center of gravity G separated from the upper or lowerend of the coil spring 55 is within approximately half of the verticallength of the spring 55), the aforementioned rotation moment, P×L, canbe reduced. Consequently, the load that must be applied to operate thehorn-switching mechanism can be made smaller than heretofore. Of course,if the above-described range is exceeded, unwanted operation of the horndue to swinging movement of the air bag system cannot be preventedunless springs of higher spring constants are used. Hence, lessadvantages will be produced.

In the above-described embodiments, the coil springs 55 are used asexamples of the biasing means. Leaf springs may be employed instead.

What is claimed is:
 1. A steering wheel, comprising: a steering wheelmain body on a steering wheel main body side, the steering wheel mainbody including a ring portion, a boss portion arranged at a center ofthe ring portion, and a plurality of spoke portions that join the bossportion and the ring portion; a horn-switch mechanism, the horn-switchmechanism having a stationary contact, a movable contact, a biasingmember, a limiting member, and a support plate having a plurality ofbase body portions and a connecting portion connected to the steeringwheel main body and arranged downward of the plurality of base bodyportions; and an air bag assembly on an air bag assembly side andarranged over the steering wheel main body by connecting the connectingportion to the steering wheel main body, the air bag assembly includingan air bag formed into a bag shape and folded in an inflatable manner,an inflator that feeds the air bag with an inflating gas, a pad coveringthe folded air bag, and a bag holder that holds the air bag, theinflator, and the pad, and a plurality of mounting portions extendinglaterally outward of the inflator, wherein: the air bag assembly isbiased upward by the biasing member and a distance of the air bagassembly from the steering wheel main body is limited by the limitingmember, the movable contact is arranged on the air bag assembly side andthe stationary contact is arranged on the steering wheel main body sideand, when the biasing member is compressed by depressing the pad, themovable contact is contacted to the stationary contact to activate ahorn, the plurality of base body portions are arranged downward of theplurality of mounting portions, the biasing member and the limitingmember are arranged between a respective mounting portion and base bodyportions of the plurality of mounting portions and the plurality of basebody portions, and the plurality of base body portions abut and aresupported by the plurality of spoke portions.
 2. The steering wheel ofclaim 1, wherein the pad includes a top wall portion having a segment tobe broken at an inflating state of the air bag, and a side wall portionextending downwardly from an outer periphery of the top wall portion,and each of the plurality of mounting portions is arranged to projectoutwardly from the side wall portion at a lower surface side of the topwall portion.
 3. A steering wheel, comprising: a steering wheel mainbody on a steering wheel main body side, the steering wheel main bodyincluding a ring portion, a boss portion arranged at a center of thering portion, and a plurality of spoke portions that join the bossportion and the ring portion; a horn-switch mechanism, the horn-switchmechanism having a stationary contact, a movable contact, a biasingmember, a limiting member, and a support plate having a plurality ofbase body portions and a connecting portion connected to the steeringwheel main body and arranged downward of the plurality of base bodyportions; and an air bag assembly on an air bag assembly side andarranged over the steering wheel main body by connecting the connectingportion to the steering wheel main body, the air bag assembly includingan air bag formed into a bag shape and folded in an inflatable manner,an inflator that feeds the air bag with an inflating gas, a pad coveringthe folded air bag, and a bag holder that holds the air bag, theinflator, and the pad, and a plurality of mounting portions extendinglaterally outward of the inflator, wherein: the air bag assembly isbiased upward by the biasing member and a distance of the air bagassembly from the steering wheel main body is limited by the limitingmember, the movable contact is arranged on the air bag assembly side andthe stationary contact is arranged on the steering wheel main body sideand, when the biasing member is compressed by depressing the pad, themovable contact is contacted to the stationary contact to activate ahorn, the plurality of base body portions are arranged downward of theplurality of mounting portions, the biasing member and the limitingmember are arranged between a respective mounting portion and base bodyportions of the plurality of mounting portions and the plurality of basebody portions, and the stationary contact is arranged at each of theplurality of base body portions, and the movable contact is arranged ateach of the plurality of mounting portions.
 4. The steering wheel ofclaim 3, wherein the pad includes a top wall portion having a segment tobe broken at an inflating state of the air bag, and a side wall portionextending downwardly from an outer periphery of the top wall portion,and each of the plurality of mounting portions is arranged to projectoutwardly from the side wall portion at a lower surface side of the topwall portion.
 5. A steering wheel, comprising: a steering wheel mainbody on a steering wheel main body side, the steering wheel main bodyincluding a ring portion, a boss portion arranged at a center of thering portion, and a plurality of spoke portions that join the bossportion and the ring portion; a horn-switch mechanism, the horn-switchmechanism having a stationary contact, a movable contact, a biasingmember, a limiting member, and a support plate having a plurality ofbase body portions and a connecting portion connected to the steeringwheel main body and arranged downward of the plurality of base bodyportions; and an air bag assembly on an air bag assembly side andarranged over the steering wheel main body by connecting the connectingportion to the steering wheel main body, the air bag assembly includingan air bag formed into a bag shape and folded in an inflatable manner,an inflator that feeds the air bag with an inflating gas, a pad coveringthe folded air bag, and a bag holder that holds the air bag, theinflator, and the pad, and a plurality of mounting portions extendinglaterally outward of the inflator, wherein: the air bag assembly isbiased upward by the biasing member and a distance of the air bagassembly from the steering wheel main body is limited by the limitingmember, the movable contact is arranged on the air bag assembly side andthe stationary contact is arranged on the steering wheel main body sideand, when the biasing member is compressed by depressing the pad, themovable contact is contacted to the stationary contact to activate ahorn, the plurality of base body portions are arranged downward of theplurality of mounting portions, the biasing member and the limitingmember are arranged between a respective mounting portion and base bodyportions of the plurality of mounting portions and the plurality of basebody portions, and the support plate includes connecting rod portionsthat connect the plurality of base body portions.
 6. The steering wheelof claim 5, wherein the pad includes a top wall portion having a segmentto be broken at an inflating state of the air bag, and a side wallportion extending downwardly from an outer periphery of the top wallportion, and each of the plurality of mounting portions is arranged toproject outwardly from the side wall portion at a lower surface side ofthe top wall portion.
 7. A steering wheel, comprising: a steering wheelmain body on a steering wheel main body side, the steering wheel mainbody including a ring portion, a boss portion arranged at a center ofthe ring portion, and a plurality of spoke portions that join the bossportion and the ring portion; a horn-switch mechanism, the horn-switchmechanism having a stationary contact, a movable contact, a biasingmember, a limiting member, and a support plate having a plurality ofbase body portions and a connecting portion connected to the steeringwheel main body and arranged downward of the plurality of base bodyportions; and an air bag assembly on an air bag assembly side andarranged over the steering wheel main body by connecting the connectingportion to the steering wheel main body, the air bag assembly includingan air bag formed into a bag shape and folded in an inflatable manner,an inflator that feeds the air bag with an inflating gas, a pad coveringthe folded air bag, and a bag holder that holds the air bag, theinflator, and the pad, and a plurality of mounting portions extendinglaterally outward of the inflator, wherein: the air bag assembly isbiased upward by the biasing member and a distance of the air bagassembly from the steering wheel main body is limited by the limitingmember, the movable contact is arranged on the air bag assembly side andthe stationary contact is arranged on the steering wheel main body sideand, when the biasing member is compressed by depressing the pad, themovable contact is contacted to the stationary contact to activate ahorn, the plurality of base body portions are arranged downward of theplurality of mounting portions, the biasing member and the limitingmember are arranged between a respective mounting portion and base bodyportions of the plurality of mounting portions and the plurality of basebody portions, and the bag holder includes a lateral plate portion and aplurality of interconnecting plate portions extending upward from edgesof the lateral plate portion, the lateral plate portion has an insertionhole into which the inflator is inserted, each of the plurality ofinterconnecting plate portions has each of the plurality of mountingportions in an outwardly extended position from a top end of each of theplurality of interconnecting plate portions.
 8. The steering wheel ofclaim 7, wherein the pad includes a top wall portion having a segment tobe broken at an inflating state of the air bag, and a side wall portionextending downwardly from an outer periphery of the top wall portion,and each of the plurality of mounting portions is arranged to projectoutwardly from the side wall portion at a lower surface side of the topwall portion.